Hitherto, as a guide device serving as a guide portion of machine tools or various industrial robots, there has been known a guide device including a track rail, which has a linear shape or an arc shape and has a raceway surface for balls along a longitudinal direction, and a moving block, which is assembled to the track rail through intermediation of a plurality of balls. The moving block includes a load raceway surface opposed to the raceway surface of the track rail, and includes a circulation path for endlessly circulating the large number of balls which roll while bearing a load between the load raceway surface and the raceway surface of the track rail. Through circulation of the balls in the endless circulation path, the moving block can continuously move along an entire length of the track rail.
Typically, the track rail is fixed to a base portion such as a bed or a column of, for example, a machine tool by fastening of fixing bolts. Therefore, the track rail has bolt mounting holes penetrating therethrough, which are arrayed at predetermined intervals along a longitudinal direction of the track rail and are configured to allow the fixing bolts to be inserted therethrough. When a head portion of the fixing bolt projects on the track rail, movement of the moving block along the track rail is hindered. Therefore, an inside of the bolt mounting hole has two stages including a small-diameter portion and a large-diameter portion. The small-diameter portion has an inner diameter which is slightly larger than a nominal diameter of the bolt. The large-diameter portion has an inner diameter which is slightly larger than the bolt head portion. That is, the large-diameter portion serves as a receiving portion for the bolt head portion to prevent the bolt head portion from projecting on the surface of the track rail.
Meanwhile, in order to prevent entry of a foreign object adhering to the track rail into the moving block, seal members which are brought into slide contact with the track rail are provided in a periphery of the moving block. Those seal members remove the foreign object adhering to the surface of the track rail along with movement of the moving block. However, when the bolt mounting holes are formed in the track rail, the foreign object may enter the moving block through the bolt mounting holes. Moreover, the seal members are held in contact with the surface of the track rail with a certain degree of a fastening force. Therefore, when the bolt mounting holes are present, distal end portions of the seal members are abraded by opening edges of the bolt mounting holes, which may disadvantageously cause degradation of the seal members in an early stage.
Therefore, when the guide device is to be used in an environment in which the foreign object is liable to adhere to the track rail, for example, as disclosed in Patent Literature 1, closure caps are press-fitted into the bolt mounting holes of the track rail to close the bolt mounting holes with the closure caps. As a specific method of press-fitting, the following method is employed. A distal end of the closure cap is gently pressed into the bolt mounting hole, and a back plate is placed on the closure cap. The back plate is repeatedly hit with a tool such as a hammer to completely embed the closure cap in the bolt mounting hole. With such method, an upper surface of the closure cappress-fitted into the bolt mounting hole forms a surface in flush with a surface of the track rail. With this, enhancement in sealing between the seal members and the track rail is expected.